Scientists Rediscover Venus to Glean Universe for Earth-like Planets

Astronomers have decided to take a closer look at Venus to learn more about the planet. They're using a new optical device installed on the Italian National Telescope to measure Venus' precise gravitational pull on the sun.

So far, astronomers have discovered more than 1,700 exoplanets, some as far as hundreds of light-years away. Most of these exoplanets were discovered with the transit method, which measures a decrease in brightness when a planet orbiting a distant star passes in front of that star, moving between it and Earth. This method allows scientists to see which planets are located in the habitable zone so that they can target specific ones for future study.

Yet now, the scientists are developing the optical device in order to better catalogue these exoplanets. The new laser-based technology known as the green astro-comb, and is for use with the radial velocity method. This method offers complementary information about the mass of distant planets. In fact, scientists can use this technique to discover whether exoplanets are rocky worlds like Earth or are gas giants like Jupiter.

The radial velocity method works by measuring how exoplanet gravity changes the light emitted from its star. As exoplanets circle a star, their gravitation tugs at the star changing the speed with which is moves toward or away from Earth by a small amount. This motion-based frequency change is known as the Doppler shift, and astronomers can measure it by capturing the spectrum of a star on the pixels of a digital camera and watching how it changes over time. The new astro-comb should be able to detect Doppler shifts as small as 10 centimeters per second.

Now, the scientists plan to test the astro-comb by pointing it at our sun, analyzing its spectrum to see if they can find Venus and rediscover its characteristic period of revolution, its size, its mass and its composition.

"We know a lot about Venus, and we can compare our answers to what we already know, so we are more confident about our answers when we point our spectrographs at distant stars," said Chih-Hao Li, one of the researchers, in a news release. "We will look at the thousands of potential exoplanets identified by the Kepler satellite telescope by the transit method. Together, our two methods can tell us a lot about those worlds."

The findings will be present at The Optical Society's 98th Annual Meeting, Frontiers in Optics.